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Floor insulation is a hot topic right now, along with other ways to insulate your home. The flooring is one of the main places where heat loss occurs. This is due to gaps in floors, baseboards and drafts around pipes.
“Insulating and improving the airtightness of your floor can be a good first step towards a more comfortable home,” says Chayley Collis at Green building store. “The ground floors can be incredibly cold and contribute greatly to the discomfort of the inhabitants.”
Insulating your home won’t just keep it warm. It will also help reduce your property’s carbon emissions and reduce utility bills. According to the Energy Saving Trust, installing floor insulation in a typical semi-detached house could save you around £50 a year on energy bills. This is how 175 kg of carbon dioxide.
For thermal performance, it suffices to insulate the ground floor of a dwelling. If you live in an apartment or upstairs in a townhouse, you generally don’t need to insulate your floor space. However, you should consider insulating all floors above unheated spaces, such as garages, as you could lose a lot of heat through these.
Some people living in older apartments or first floor maisonettes can improve the acoustic performance of their floors by using floor insulation. “If you want to improve the acoustic performance of your interior floors, make sure the insulation you choose provides acoustic benefits,” says Bradley Hirst, technical services manager at Knauf insulation. “Mineral wool insulation works well to reduce noise transfer between living areas, bedrooms and bathrooms.”
What is Floor Insulation?
Floor insulation is a method of adding materials under the floorboards if your house has a suspended wooden floor. It can also be added above solid ground, such as concrete. The process also involves blocking drafts by properly sealing gaps in flooring and baseboards.
“The insulation materials used will resist heat transfer and reduce the amount of heat lost in your home,” says Thomas Goodman, real estate and construction expert at MyJobQuote.
According to the Energy Saving Trust, a typical installation can cost you between £520 and £1,300, depending on the circumstances. The upfront price might seem steep considering the saving is only around £50 per year. But it should last the life of your home with very little maintenance cost.
What are the best floor insulation options?
We take a look at what’s available and the pros and cons of each type.
Glass or rock mineral wool slabs
A semi-rigid material, glass mineral wool is made from recycled glass, sand, limestone and soda ash. While rock mineral wool is made from volcanic rock, basalt, dolomite and recycled slag from the steel industry.
- Best for Use in suspended wood floors, as it is lightweight, easy to cut. It is more forgiving when packing between unevenly spaced or warped joists.
- Benefits In addition to having excellent thermal performance, it is incombustible. Thus, it will not add to the development or spread of fire should it occur. It’s also easy to cut, light to maneuver, and measurements don’t need to be as precise as with rigid foam boards.
- The negatives Less rigid construction means more support is needed to hold this insulation in place. A net or battens crossing the joists must be installed beforehand. This makes for a longer installation compared to rigid panels.
- The cost An average pack of 12 mineral wool tiles will cost around £30 and will cover around 9m².
Sheet floor insulation
Sheet floor insulation is a roll of unfaced mineral glass wool or fiberglass.
- Best for Fiberglass blankets are best used when wrapping between joists in suspended floors. It is not suitable for solid flooring as its uneven consistency will make your chosen flooring uneven.
- Benefits Easy to pack between joists with minimal measuring. Affordable and little expertise needed for installation.
- The negatives Cumbersome to move around and the glass spores are easily dislodged from the roller itself. Appropriate PPE clothing is required to work with.
- The cost A roll will cost around £20 and will cover around 14m².
Rigid foam insulation
Foam boards are made from foam inside and then covered with plastic, aluminum or plasterboard.
- Best for Rigid foam insulation can be used for both suspended and solid floors. The thickness of the boards will vary greatly depending on the type of floor they insulate. It is particularly easy to lay on solid ground.
- Benefits Easy to cut, shape and move from area to area.
- The negatives A less forgiving material than other less rigid forms of insulation. Accurate measuring and cutting are essential.
- The cost Around £10-15 per m²depending on the thickness of the insulation.
Spray foam insulation
Spray foam insulation is liquid foam that is sprayed between the joists of a suspended wooden floor. The foam expands and sets into a top insulating layer.
- Best for Bulky spaces or if you want to insulate your home without having to lift the floorboards.
- Benefits Will completely seal between even the most uneven and warped joists without leaving a gap. It also offers exceptional thermal resistance. There’s even a robotics company called Q-Bot that uses remote-controlled robots to spray insulation into the void beneath the floor, causing minimal disruption.
- The negatives Can only be installed by qualified professionals.
- The cost An average floor will cost around £525. This will naturally vary depending on the size of the floor. Expect to pay more if you use Q-Bot.
Multifoil is a type of insulation made up of layers of aluminum foil and wadding.
- Best for Solid floor constructions, but can also be used for suspended wooden floors.
- Benefits Multifoil insulation has a long life – typically 50 years. It is easy to handle, lightweight, flexible and contains no harmful fibers. This means it can be installed without specialist tools or PPE. If you’re worried about head height being limited after insulation and flooring have been installed, SuperFOIL sells a particularly thin multifoil called SFUF. Measuring just 6mm thick, it still delivers high thermal performance. A reflective foil prevents heat loss.
- The negatives Usually costs more than other insulation materials.
- The cost Multifoil insulation starts at around £7.20 per m².
Drafts occur where there are gaps in your home’s construction, such as floors and baseboards.
- The best product to use? Flexible plasters, decorative caulks, or putty-based products can all tolerate movement. This makes them perfect for blocking cracks in flooring and baseboards, which tend to shrink, expand or shift slightly with daily use.
- Benefits Blocking unwanted spaces that let cold air in and warm air out of your home will save hot air. This means you’ll use less energy to heat your home and save money on your energy bills. It will also help create a warm and comfortable living environment.
- The negatives Be careful in rooms that need good ventilation (such as bathrooms, kitchens and laundry rooms), where a lot of humidity is produced.
- The cost According to the Energy Saving Trust, budget around £200 to add professional draft protection to a typical semi-detached property. Do-it-yourself against drafts will be cheaper.
Rugs and carpets
A rug on the floor will help you feel warm underfoot and block drafts. But this will not significantly reduce heat loss through the floor. Carpets can provide some level of insulation. To avoid optimal heat loss, you should always install insulation under carpets. This ensures that your home is protected as much as possible.
- Best for Use in living rooms and bedrooms.
- Benefits Carpeted floors are good insulators, especially when paired with a thick, insulating layer of underlay underneath.
- The negatives Not practical for high traffic spaces or areas prone to moisture and dirt. These include entrance hallways, kitchens and bathrooms.
- The cost Mats can cost between £5 and £30 per m². Carpet underlay costs an additional £3.50 to £28 per m².
Is floor insulation enough on its own?
Insulating your floors is a great start to reducing your home’s carbon emissions and lowering your utility bills. It will work best when used in tandem with other types of insulation, such as cavity wall insulation and roof and attic insulation. “It’s called top and tail insulation,” says Thomas Goodman. “As a general rule, the more insulation you have in your home, the warmer and more efficient it will be.”
What U-value for flooring is required?
The amount of insulation you need will depend on the current U-value of your floor installation. According to the Energy Saving Trust, if you live in England or Wales, the floor should achieve a U-value of 0.25 W/m²K. Less if possible, to meet building regulations. The U-value is a measure of how quickly heat will travel through the ground. To achieve this standard, the Energy Saving Trust recommends installing at least 70mm of high performance foam insulation or 150mm of mineral wool. This will vary depending on the insulation material and brand chosen, as well as the type, shape and size of the floor.